Generally the invention relates to the field of solvent bonding. Specifically, the invention relates to the action of the solvent itself to create a bond between at least two parts. In terms of the knowledge and skills involved, it is distinguished from such fields as the field of designing parts which may be bonded together to perform specific purposes, the field of devices to introduce solvent to parts for bonding, and the field of particular chemicals to serve as a solvent.
For many years the technique of joining two parts together through the action of a solvent has been utilized with varying degrees of success. The basic technique simply involves the introduction of a solvent to two surfaces which are then dissolved and which bond together after the solvent evaporates away. Perhaps due to the simplistic basis for the technique of solvent bonding, efforts at refining the technique have generally been based upon an assumption that the resultant bond should obviously be as strong as possible. Importantly, the present invention departs from this assumption and provides a technique through which bonds having a variety of characteristics can be repeatedly created. From the designer's perspective, the invention allows the particular characteristic (or combinations thereof) to be predetermined as appropriate for the particular application. The chosen characteristics are then created automatically through the action of the solvent itself. In so doing, this technique allows the designer the freedom to choose an end result which may have characteristics within a broad range of possibilities. These characteristics include--but of course, are not limited to--the resultant bond's: strength, ability to seal, appearance, failure mode, etc. Significantly, the present invention affords the designer the opportunity to confidently know that the characteristics will be automatically created through the action of the solvent itself rather than through some manipulation or supervision at the assembly level.
Prior to the present invention, those skilled in the art of solvent bonding, seemed to focus their efforts in directions which might be characterized as either: i) efforts designed to control incidental effects of the bonding process, or ii) efforts to externally control the process to create the bond. This is perhaps due to the preconceptions of those involved that, of course, the strongest bond possible was always desired. Representative of the types of improvements directed toward controlling the incidental effects of the bonding process are several patents. In. U.S. Pat. No 4,651,382 to Krolick, a blocking moat design was disclosed to act as a barrier to prevent solvent from penetrating undesirable areas. In applications such as a door hinge, the moat served to avoid the introduction of the solvent to the moveable parts of the hinge itself and thus avoid an undesirable incidental effect of the solvent bonding process. Similarly, U.S. Pat. Nos. 4,256,333, 4,181,549, and 4,137,117 each disclosed designs for a solvent bonded joint which avoided the incidental effect of contamination by the solvent of medically pure fluids. In all of these cases, the inventors designed elements which would act to control some consequential effect of the bonding process. Notably, none of these inventions concern themselves with the characteristics of the resultant bond or--more to the point--with the automatic creation of specific bond characteristics.
The second group of directions those skilled in the art have taken has been the direction of externally controlling the bonding process. Interestingly in many of these types of improvements, the characteristics of the bond itself are not even mentioned. Representative of this direction is U.S. Pat. No. 4,595,446 to Newkirk for an apparatus which automates the application of solvent. Through Newkirk's invention, improvement to devices which create the bond are disclosed. Again, no consideration is given to the characteristics of the resultant bond itself. Rather, through lack of comment, there is a tacit acknowledgement that when it comes to the resultant bond, the solvent itself creates a bond having some characteristics and those characteristics are out of the designer's control.
The presupposition prior to the present invention that the characteristics of the bond itself were not controllable by the designer was most likely due to a bias by those skilled in the art to create the strongest bond in all instances. This is perhaps understood once it is realized that the creation of the solvent bond was generally accomplished as an assembly function. Thus, assemblers created the bond. These persons usually not only possessed a lesser degree of skill than designers but they usually also had little latitude in impacting improvements to the designs. These effects therefore lead to a focus on trial and error efforts or on solvent metering devices rather than unique part designs. This trial and error based level of expertise resulted in a field which may be characterized by slow, incremental improvement rather than dramatic innovation on a wide scale. The technology simply was not viewed as a highly sophisticated technology, rather it was viewed as a rather simple art in which minor improvements are the norm. Surprisingly, the need for and usefulness of bonds having variable characteristics which are automatically created through the action of the solvent has existed for some time. It is also true that the implementing arts and elements have been readily available throughout this time as well. Those skilled in the art simply did not appreciate the aspect of allowing for variable characteristics in the bond because they tended to assume that the strongest bond possible was always desired. This teaching away from the technical direction of the present invention was perhaps bolstered by unrelated arts such as heat bonding materials in which it is also assumed that the strongest bond possible is the most desirable.